Ammonium nitrate explosive



July 20, 1937. s. L. HANDFORTH ET AL 2,087,285

AMMONIUM NITRATE EXPLOSIVE Filed Jan. 10, 1935 Fig.2

Jfanley LHcmd/or/h Snventora Norman Johnson (Ittorneg Patented July 20,1937 UlTED STATES PATENT OFFH AIVIMIONIUBI NITRATE EXPLO SIVE awareApplication January 10, 1935, Serial -No. 1,108

11 Claims.

This invention relates to low density dynamite compositionscontainingammonium nitrate and, more particularly, to such explosives havingimproved properties adapting them for use in the blasting down of coaland other material.

The developments in recent years in explosives of the permissible typefor use in coal mining have been particularly directed toward lowdensity ammonia dynamites, usually with ammonium nitrate contentsbetween 50 and 80%. Such explosives allowed a more economical and moreeflicient loading of bore holes with a decrease in the shattering effectand the production of a high proportion of lump coal.

The attempts to attain low density properties in ammonium nitratedynamites have been very successful, and this has resulted largely fromthe introduction of low density combustible ingredients, for examplebagasse pith, balsa wood, cornstalk pith, impregnated ingredients,cereal products, and the like.

While a new type of commercial blasting explosive has resulted from thelowering of the density of the ammonium nitrate dynamites,

problems have been introduced in the control of the properties of thefinished explosive. The use of very low density explosives meant, forexample, a high ratio of wrapper weight per weight of actual explosiveand consequently a dynamite quitedeficient in oxygen. The fumeproperties, therefore, were not as satisfactory as would otherwise havebeen the case. Likewise, a given amount of very light weightcarbonaceous material in many cases absorbed nitroglycerin more than adenser ingredient, and the sensitiveness of the explosive to detonationtended to become lower.

A more satisfactory solution of the low density problem would beattained if the desired effect could be brought about, at least in part,by control of the density of the ammonium nitrate since this is thepredominating ingredient in dynamites of the ammonia permissible type.The use of a lower density ammonium nitrate would permit a reduction ofthe combustible content and in this way improvement could be broughtabout in fume properties, sensitiveness, and strength, since ammoniumnitrate is an explosive material of relatively high strength. Efforts inthis direction up to the present time, however, have not given a productsufficiently satisfactory to be introduced successfully into commercialpractice.

The object of our invention is a new and improved ammonium nitrateexplosive characterized by relatively low density. A further object issuch an explosive in which the low density property is attained to agreater degree than has been possible heretofore without introduction ofdisadvantageous effects. A further object is an explosive of the naturedescribed in which the desired result is brought about by theutilization of a new type of material. Additional objects will becomeapparent as the invention is further described.

We have found that the foregoing objects are accomplished by theintroduction into dynamite compositions of solid particles of ammoniumnitrate having a relatively low apparent density as a result of thespraying of a highly concentrated solution of said salt at a temperaturenot substantially above the solidification point of the solution. Suchan ammonium nitrate will have an apparent density not higher than 0.80,between 0.50 and 0.80 for example. By reason of the conditions underwhich the ammonium nitrate is produced, the separate particles willpossess irregular shapes, very markedly distorted from the spherical andfrom the natural crystalline forms of ammonium nitrate.

The effect of these distorted forms of the individual particles is thatthe material is permitted to pack to a density substantially lower thanit has heretofore been possible to attain satisfactorily and in suchmanner that the low density efiect is not lost with continued storageunder the slight pressures resulting from such storage.

The method by which our ammonium nitrate ingredient of irregular form isprepared is described in the copending application of S. L. Handforthand K. C. Simon, Serial No. 1,109 filed January 10, 1935. According tothis process, highly concentrated ammonium nitrate solution, of astrength above 98% NH4NO3 for example, is sprayed by means of arevolving disc, the temperature of the solution prior to passage throughthe disc being maintained relatively close to the solidification point,but sufficiently high to assure fluidity during said passage. In thisway, a substantially solid product of the irregular shape desired andpractically free from water is obtained. Using the new form of ammoniumnitrate described, sufiiciently low densities will be obtained so thatthe weight of a 1%X8" eartridge will be less than 146 grams andpreferably less than 125 grams.

Symmes (U. S. Patent 1,613,335) has disclosed the utilization inexplosives of ammonium nitrate in the form of spherical grains havinginternal cavities and that such form of ammonium nitrate may be producedby a spraying process.

Champney (U. S. Patent 1,924,912) likewise discloses a low densitydynamite containing crystalline ammonium nitrate of low density.

The irregular and distorted product employed in our invention isaltogether different in appearance from the products obtained heretoforeand possesses very characteristic low density properties that arepermanent in nature. The process by which our product is obtained iscontrolled so that substantially solid particles result that aredistorted from the shapes that would naturally be anticipated, both fromthe spherical globules of the Symmes patent, and the crystalline formsof the Champney patent.

The low density ammonia dynamites heretofore considered so important inthe mining of coal and other soft material for blasting have containednitroglycerin as sensitizing agent, low density combustible ingredientsbeing necessary as absorbents. According to our invention, solid organicexplosive compounds of the desired degree of sensitiveness may replacethe nitroglycerin, since the low density efi'ect may be and is desirablyobtained, at least in part, from the low density ammonium nitrate. Assuch sensitizing solid ingredients, we may use, for example,nitrostarch, pentaeryt-hritol tetranitrate, trinitrotoluene, and thelike. The presence of high percentages of low density carbonaceousmaterials in such compositions is undesirable because of their adverseeffect on the oxygen balance, the

above solid explosive compounds themselves being very deficient inoxygen. The use of low density ammonium nitrate is very advantageous forthe purpose since this material contains a considerable oxygen excess.

By way of illustration, the following examples show the advantages ofour new product.

Formula B shows that to attain the same low density effect in theexplosive by variation in combustible content would mean a. decidedsacriflee in strength, sensitiveness, and fumes.

Similar formulas to illustrate our invention and using nitrostarch andtrinitrotoluene as sensitizing ingredient are shown briefly below.

As before the same density could be maintained, if desired, and animprovement obtained in strength and fumes.

In the foregoing description of our invention, it has been shown thatgreatly improved properties in ammonium nitrate dynamites are obtainedby the replacement of the ammonium nitrate of the prior art by the newproduct obtained by the spraying of jhighly concentrated ammoniumnitrate solutions under proper temperature conditions. To ngake thedistinction clearer, the low density ammonium nitrate used by us isillustrated in Figures 1 and 2. Figure 1 shows the form of the fineparticles and their irregular distorted shapes, while Figure 2illustrates coars r particles, the particles being magnifiedapproinmately 30 times in both figures.

A B O Nitroglycerin 14. 14. 0% l4. 0% crystallized ammonium nitrate 57.0 52. 0 Sprayed cooled ammonium nitrate" 57. 0 Sodium nitrate 9. 5 9. 59. 5 Bagasse pith 9. 5 14. 5 9. 5 Flaked cereal produc 9. 0 9. 0 9. 0

ice 0.5 0. 5 0. 5

hnlk 0. 5 0. 5 0. 5

Ctgs./50 lbs 225 250 250 Oxygen balance. 7. 4 14. 7 6. 9 Oxy. bal.wrapped 27. 2 -35.9 29. 0 Weight strength-.- 56 42 54 sensitiveness 10 610" Fumes -Jiters CO/lb-- 54 72 58 Ammonium nitrate CrystallizedSpray-cooled" Purity 97. 9 99. 2 Apparent density 0. 85 0. 73 Fineness:

On 35mesh screen percent. 5 3

Passing IOU-mesh screen .percent 53 60 In the formulas presented, Arepresents a low density dynamite containing the crystallized ammoniumnitrate of the prior art, while C gives an exactly similar formulaexcept that the new type of sprayed ammonium nitrate is used. instead.It will be seen that the use of the low density ammonium nitrate allowsthe attainment of 250 sticks per 50 lb. casein place of 225 sticks. andat the same time gives substantially the same properties with respect.to oxygen balance, strength, fumes, and sensitiveness.

It will be seen that our invention makes it possible to produce ammoniadynamites characterized by low density and having considerableadvantages over similar explosives previously made. Improvement instrength may be obtained, for example, with the same formula or the samestrength may be obtained with a decreased content of explosive.Improvement in sensitiveness and fume properties likewise result forsimilar compositions.

In the description of our invention, it has been described as directedtoward the production of low density explosives. It will be understoodthat such explosives may be produced of varying velocities by the methodof using coarse or fine ammonium nitrate grains according as relativelylow or high velocities are desired. The utilization of both types ofgranulations in low density dynamites is contemplated by our invention.

It has been indicated in the foregoing also that an ammonium nitrateproduct is used having an apparent density lower than 0.80. This densityvalue is determined by filling a brass cylinder of an inside diameter of2" with five successive increments of 2.5" each of ammonium nitrate,pressing each addition under a dead weight of 16 lbs., and obtaining theapparent density from the weight and volume of the pressed ammoniumnitrate in the cylinder,

While our invention has been'described fully in the foregoing, it willbe apparent to those skilled in the explosive art that many changes maybe made in the compositions cited and in the details of procedurewithout departing from the spirit of the invention. We intend to belimited, therefore, only as indicated in the follpwin patent claims.

We claim:

1. A blasting explosive composition characterized by relatively lowdensity and comprising an i and ammonium nitrate in the form of substan-'tially solid particles *of" irregular shapes, said ammonium nitratehaving an apparent density lower than 0.80 as a result of the sprayingof a highly concentrated solution of said salt at a temperature notgreatly above the solidification point of the solution.

5. The explosive composition of claim 4, 'in which the explosivecompound is a liquid aliphatic nitric ester.

6. The explosive composition of claim 4, in which the explosive compoundis nitroglycerin.

7. An explosive composition characterized by relatively low density andcomprising an explosive liquid nitric ester, a carbonaceous combustibleingredient, and ammonium nitrate in the form of substantially solidparticles of a shape markedly distorted from that of spheres and fromthe natural crystalline forms of ammonium nitrate,

said ammonium nitrate having an apparent density lower than 0.80 as aresult of the spraying of a highly concentrated solution of said salt ata temperature not greatly above the solidification point of thesolution.

8. The explosive composition of claim 7, in which the liquid nitricester is nitroglycerin.

9. An explosive composition having a density such that a 1 /4 X 8"cartridge weighs less than 146 grams, said explosive comprising a liquidexplosive nitric ester, a carbonaceous combustible ingredient, andammonium nitrate in the form of particles of a shape markedly distortedfrom that of spheres and from the natural crystalline forms of ammoniumnitrate as a result of the spraying of a highly ooncentratedsolutionofsaid salt at a temperature not greatly above the solidification point ofthe solution.

10. The explosive composition of claim 9, in which the ammonium nitratehas an apparent density lower than 0.80.

11. A blasting explosive composition characterized by relatively lowdensity and comprising an organic explosive compound as sensitizingagent, and ammonium nitrate in the form of substantially solid particlesof a shape markedly distorted from that of spheres and having arelatively low density as the result of the spraying of v a highlyconcentrated solution of said salt at a temperature not greatly abovethe solidification point of the solution.

STANLEY L. HANDFORTH. NORMAN GARDNER JOHNSON.

CERTIFICATE OF CORRECTION. Patent No. 2,087,285. July 20, 195?.

STANLEY L. HANDFORTH, ET AL.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiringcorrection as follows: g z, Secondcolumn, line 5, beginning with the table strike out all to and includingthe word and period "sensitiveness." in line 55, and insert the sameafter line l l, in the first column, same page, following the words andperiod "new product."; and that the said Letters Patent should be readwith this correction therein that the same may conform to the record ofthe case in the Patent Office.

Signed and sealed this 25th day of January, A. D. 1958.

Henry Van Arsdale, (Seal) Acting Commissioner of Patents.

. CERTIFICATE OF CORRECTION. Patent No. 2,087,285. July 20, 1957.

STANLEY L. HANDFORTH, ET'AL.

It is --hereby oertii iedthat error appears in the printedsnecifioati'on of the above numbered patent requiring'correetion asfollows P g 8.600116. column, line 5, beginning with the table strikeout. all to and inoluding the word. and period "sensitiveness.. in line55, and. insert the same after line hl, in the fir'st column, same page,following the words and period "new product."; and that the seid'LettersPatent should be read with this correction thereinthat the same mayconform to the record ofthe case in the Patent Office.

signed and sealed this 25th day of January A. D. 1958.

Henry Van Arsdele;

(Seal) Aoting Commissioner of Patents.

